Leave plenty of spare cable at the cabinet end, Cat5e/Cat6 is cheap as chips and it's always good to have plenty of spare to route neatly and tie down in the rack. To get a tidy patch, flip the panel up and rack it back to front, so you can get the lengths perfect and have a firm surface to punch down to. Moley's spot on about doubling up, running singles is pointless when a single gang box takes a pair and if you don't need more data points now, you will in the future (I learned that the hard way, ending up with numerous 4-wire splitters on the wall and in the cabinet).